The recent trend in the electrolytic industry is to employ an electrode comprising a substrate having high stability under anode conditions, e.g., titanium and titanium alloys, coated with an electrode catalyst substance, particularly the oxides of the platinum group metals, in place of soluble electrodes as exemplified by carbon. This electrode, called a dimensionally stable anode (DSA) or a dimensionally stable electrode (DSE), is used in a variety of industrial electrolytic processes including production of oxygen gas by electrolysis of water and production of halogen or alkali hydroxide by electrolysis of an aqueous solution of metal halide, because of its excellent electrolytic characteristics and durability, as described in U.S. Pat. Nos. 3,711,385 and 3,632,498.
The anode substance plays an important role in production of ozone gas and peroxides utilizing the anodic electrolytic reaction and in organic electrolysis. In the electrolytic reaction for the production of ozone gas, the electric potential is high, and even if DSA is used, low potential electrolytic reactions predominate. Thus, DSA is unsuitable for the electrolytic production of ozone gas, and only a titanium electrode coated with platinum is utilized.
In the electrolysis for the production of ozone gas, an anodic catalytic substance which can be used in place of DSA with an increase in the efficiency of operation is needed. Thus, various investigations have been made not only in regard to electrode catalysts but also with respect to the electrode and cell structure where lead, lead oxide, carbon, etc. are used as electrode substances, as J. Elec. Chem. Soc., 132 p. 367 ff. (1985) and U.S. Pat. No. 4,416,747.
In the use of an electrode containing lead dioxide for the production of ozone, durability and mechanical strength of the electrode are poor and the lead dioxide electrode catalyst has a relatively high electrolytic voltage which increases the amount of electric power consumed.
The present inventors have proposed various improvements of the lead dioxide-coated electrode. However, the improved electrodes previously proposed by the present inventors are still not satisfactory in that a decrease in electrolytic voltage ascribable to the efficiency of the catalyst itself was insufficient, while an increase in current efficiency could not be achieved because the material to be electrolyzed in an electrolytic solution is not in sufficient contact with the active substance on the electrode. Furthermore, if the electrode active substance is too dense, gas is drawn insufficiently resulting in a higher electrolytic voltage.